i would get up early and have breakfast at the “café blau” near the english department of the university – best breakfast in town. after that i would walk through the city, maybe cross the rhine and a look at bonn-beuel at the other side of the river. depending on the weather one should definetely take the time and go to the “rheinauen” and the “post-tower”. i would basically stroll along the city. i have a lot of favourite places in this city but you need more than a single saturday to experience the whole city.